The ATSC transmission scheme set out in the ATSC A/53 Standard involves the use of 8-VSB modulation in transmitting terrestrial broadcasts for digital television receivers. An ATSC A/53 field (an ATSC A/53 frame has odd field and an even field) contains a field sync segment and 312 data segments each beginning with a segment sync. The data segments also include main data. ATSC A/53 is optimized for fixed reception.
Unfortunately, transmissions according to this standard are not robust enough against doppler shift and multipath radio interference in mobile environments because this standard is designed for slowly varying signal conditions. In order to provide robust reception in spite of doppler shifts and multipath radio interference in mobile environments, additional channel coding mechanisms are introduced in the ATSC A/153 Standard to protect the signal.
The A/153 Standard describes the ATSC Mobile DTV system referred to in the Standard as the ATSC mobile/handheld (M/H) system. The M/H system provides mobile/pedestrian/handheld broadcasting services using a portion of the ATSC 8-VSB payload, while the remainder is still available for HD and/or multiple SD television services. The M/H system is a dual-stream system that includes the ATSC service multiplex for existing digital television services and the M/H service multiplex for one or more mobile, pedestrian and handheld services.
Thus, the ATSC A/153 Standard known as ATSC-M/H is a standard for mobile digital televisions that allows television broadcasts to be received by mobile devices. ATSC-M/H is an extension to the available digital TV broadcasting standard ATSC A/53.
According to Part 2 of the A/153 Standard, one M/H Frame can carry main data (processed in accordance with the A/53 Standard) and M/H data (processed in accordance with the A/153 Standard) and is equivalent in size to exactly 20 VSB data frames. The M/H Frame consists of five consecutive Sub-Frames such that each Sub-Frame contains the same amount of data as four VSB data frames or eight A/53 data fields. Each Sub-Frame consists of sixteen consecutive M/H Slots. Each M/H Slot consists of 156 transport stream packets or equivalently 156 data segments at the symbol level, i.e., equivalent to one half of a A/53 data field. A particular Slot may contain M/H data, a combination of M/H data and main data, or only main data. If an M/H Group is transmitted during an M/H Slot, then the first 118 transport stream packets in the Slot belong to an M/H Group, and the remaining 38 packets are main data packets. If there is no M/H Group in an M/H Slot, the M/H Slot contain 156 main data packets. As in the case of an A/53 field, an A/153 field has a field sync segment and each data segment includes a segment sync portion.
Currently, a digital transmission repeater has two options. It can decode the received signal to baseband and recode the baseband data as a clean signal. Alternatively, it steps down the received signal to IF for filtering and steps up the signal at IF to RF with the same noise and multipath degradation of the received signal.
As to the first option, without additional steps, M/H data is lost when the received signal contains M/H data. As to the second option, the number of repeaters is succession is limited.
Accordingly, it is desirable to have a repeater that solves one or more of these or other problems.